title: Visualizing compaction of polysomes in bacteria.
abstract: During protein synthesis, many translating ribosomes are bound together with an mRNA molecule to form polysomes (or polyribosomes). While the spatial organization of bacterial polysomes has been well studied in vitro, little is known about how they cluster when cellular conditions are highly constrained. To better understand this, we used electron tomography, template matching, and three-dimensional modeling to analyze the supramolecular network of ribosomes after induction of translational pauses. In Escherichia coli, we overexpressed an mRNA carrying a polyproline motif known to induce pausing during translation. When working with a strain lacking transfer-messenger RNA, the principle actor in the "trans-translation" rescuing system, the cells survived the hijacking of the translation machinery but this resulted in a sharp modification of the ribosomal network. The results of our experiments demonstrate that single ribosomes are replaced with large amounts of compacted polysomes. These polysomes are highly organized, principally forming hairpins and dimers of hairpins that stack together. We propose that these spatial arrangements help maintain translation efficiency when the rescue systems are absent or overwhelmed.
authors.affiliation: Team Translation and Folding, Université de Rennes 1, UMR CNRS 6290 IGDR, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Cougot
authors.affiliation: Team Translation and Folding, Université de Rennes 1, UMR CNRS 6290 IGDR, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Anne-Elisabeth
authors.initials: AE
authors.lastname: Molza
authors.affiliation: Team Translation and Folding, Université de Rennes 1, UMR CNRS 6290 IGDR, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Jérémy
authors.initials: J
authors.lastname: Delesques
authors.affiliation: Team Translation and Folding, Université de Rennes 1, UMR CNRS 6290 IGDR, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Giudice
authors.affiliation: Team Translation and Folding, Université de Rennes 1, UMR CNRS 6290 IGDR, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Annie
authors.initials: A
authors.lastname: Cavalier
authors.affiliation: Team Translation and Folding, Université de Rennes 1, UMR CNRS 6290 IGDR, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Rolland
authors.affiliation: Université de Rennes 1, EA 1254, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Gwennola
authors.initials: G
authors.lastname: Ermel
authors.affiliation: Université de Rennes 1, EA 1254, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Carlos
authors.initials: C
authors.lastname: Blanco
authors.affiliation: Team Translation and Folding, Université de Rennes 1, UMR CNRS 6290 IGDR, Campus de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Thomas
authors.affiliation: Team Translation and Folding, Université de Rennes 1, UMR CNRS 6290 IGDR, Campus de Beaulieu, 35042 Rennes Cedex, France; Institut Universitaire de France. Electronic address: reynald.gillet@univ-rennes1.fr.
authors.forename: Reynald
authors.initials: R
authors.lastname: Gillet
mesh_terms: D055032:Electron Microscope Tomography; D004926:Escherichia coli / Q000737:chemistry* / Q000378:metabolism*; D021621:Imaging, Three-Dimensional; D046911:Macromolecular Substances / Q000737:chemistry* / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D011132:Polyribosomes / Q000737:chemistry* / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D046911:Macromolecular Substances; D010455:Peptides; D012333:RNA, Messenger; C011083:polyproline
keywords: 3D; BSA; GST; RT-PCR; TEM; bovine serum albumin; electron tomography; glutathione S-transferase; mRNA; polysomes; reverse transcription PCR; ribosome; three dimensional; tmRNA; transfer-messenger RNA; transmission electron microscopy